Bicycles and kick scooters are popular human powered vehicles and have been used by most people.
Some pedal actuate scooters have been developed as an attempt to provide substitute for regular scooters, but almost all of them are either hard to operate or clumsy, and are not acceptable to most users.
The basic arrangement of a forward sprocket wheel driven by rotating pedal cranks and coupled by an endless roller chain to a rear sprocket wheel mounted concentrically with the hub of the rear wheel of the bicycle or tricycle combines the advantages of simplicity and low friction to provide an inexpensive and efficient drive mechanism. But this conventional design has an inherent drawback, however. Rotary pedal cranks do not provide a uniformly effective conversion of the substantially linear driving force exerted by the rider into drive torque. At the top and bottom of pedal travel, drive torque is minimal. This makes the regular bicycle difficult to ride while the bicycle is slowly on uphill or muddy road even with the speed change systems. Also it is difficulty to ride bicycle with the user standing on the pedals.
Other drive mechanisms for pedaled scooters or bicycles have been used. One of the pedaled scooter in U.S. Pat. No. 6,716,141 B2 has a pair of pedals recovered by springs. U.S. Pat. No. 6,648,355 B2 is about a step driven bicycle. U.S. Pat. No. 6,648,353 B1 issued to P. Cabal describes an upright step-cycle with elliptical motion pedaling. Other pedaled drive mechanisms include U.S. Pat. No. 6,402,173 B1, U.S. Pat. No. 3,954,282, U.S. Pat. No. 3,877,724, and U.S. Pat. No. 3,375,023.